The argument from excluded diversity

A post at the excellent information source Box Turtle Bulletin has fun with what poster Rob Tisinai calls "the stoner argument against same-sex marriage". He is referring to a post by Prof. Robert John Araujo, SJ in which the good Professor opines:

[Tribe] also derides the use [of] arguments against same-sex marriage that rely on what he labels “pseudo-scientific claims.”
He does not identify the reasoning underlying these claims, but I wonder how he would consider this argument: Let us assume that two planets which have not yet been inhabited by humans are to be colonized by them; on Planet Alpha, heterosexual couples only are assigned; on Planet Beta, only homosexual couples. In one hundred years, will both islands be populated assuming that reproductive technologies are not available to either group? I suggest that Planet Alpha will be; but Planet Beta will not. Why? The basic answer is to be found in the biological complementarity of the heterosexual couple necessary for procreation that is absent in same-sex couple. This is a scientific argument, but perhaps it is, in Tribe’s estimation, counterfeit.

As Tisinai points out, there is no argument here. In Tisinai's words:

It’s just a long-winded way of saying two members of the same sex can’t conceive a child without outside help. That’s it. Granted, Araujo takes many words and a convoluted path to say it, but he never makes an argument of it — never links to it to a clear point. It’s a kind of pointless pseudo-profundity that reminds me of stoners smoking weed back in college …

Hence Tisinai's label, "the stoner argument against same-sex marriage", with funny dialogue added to demonstrate.

It is clear from what Prof. Araujo SJ writes that he is (as one would expect from a Catholic theologian) advancing a Thomist natural law position. This particular notion he advances in his non-argument is one that turns up quite a lot: best summarised as "but what if everyone acted like that?" I have seen, for example, in a debate on same-sex marriage, an elderly gentleman question the (gay) supporter of same-sex marriage in precisely those terms.

You can make the position into an argument by added an appropriate premise. Such as, for example,

No stable arrangement recognising sexual diversity is possible.

It would be an odd sort of premise, since it is clear enough that presuming opposite-sex attraction and bonding as the only acceptable option did not stop people from being sexually diverse. So it seems very odd to imply that, by including same-sex attraction and bonding within acceptable options, somehow opposite-sex attraction and bonding would be undermined.

But if one takes the view that one cannot broaden the nature of something, one can only change it, the notion makes more sense. That is, the possibility of x + y is excluded, it is only x or y. It is still a strange notion, but it is understandable in its strangeness. It becomes a case of “why does one think reality is like that?”, rather than merely “what a strange way to look at the universe!”.

The reason why comes from Aristotelian metaphysics: specifically, the four causes—in particular, the notion of final cause. The notion is that, just as the purpose of eyes is to see, the purpose of sexual organs is to procreate. So human nature has a single “proper” form—heterosexuality. From this teleological conception it follows that human nature does not have a diverse sexual form: it has a single sexual form, heterosexuality, with any divergence being improper—failing to conform to one’s proper form.

Such thinking tends to conflate causal role, biological (or other) function and sentient purpose as if they are the same sort of thing. But it also encourages an “either x or y not x and y” view of the world: that one can only have a different form with another, single defining purpose; not an expanded form.

The view not only rests on a notion of definitive form, it also rests on the notion that we have direct access to those forms. (So, in Thomism, that the form in nature and the form in our mind are the same form.) It permits the exclusion of contrary cases as “not proper” because we have direct knowledge of their defining purpose.

This is a version of the “no True Scotsman” fallacy, where the conclusion is permitted to set the ambit of its premises. So, evidence for same-sex activity, couples and parenting in nature are dismissed as “not true manifestations of sex, couple or parenting”.

Neither the claim of defining form (including purpose) nor the claim of direct understanding of that form (and so purpose) stand up to close examination. For example, the claim that the defining purpose of marriage is procreation: nonsense, the function of marriage is to allow people to build lives together. By creating that connection, marriage then becomes the prime social vehicle for raising children. But raising children does not define marriage: hence all those societies where infertility was not grounds for divorce or annulment, fertility was not a requirement for marriage and same-sex marriages have been recognised. This even without considering the very strange places such Thomist epistemic confidence led to or similar problems of natural law theory.

But, if you think in terms of definitions of “proper” form (with defining purposes) that actual instances can fall outside of, then it is not so hard to think in terms of “excluded diversity”. That the consequences of all marriages being same-sex is somehow an argument or counter-example against some marriages being same-sex.

Not that the good professor’s example works even in his own terms: it is perfectly possible to have same-sex couples “cross-pollinate” and raise children—there is even a film and a book trilogy using that premise. (It is also roughly what bonobos do).

Still, the "argument from excluded diversity" is a strange way to look at the world and that Thomist natural law thinking leads one to think in such terms is a sign that there is something wrong with it.